Variable tuned transformer



July 2, 1940. H. A. MOORE m- AL 2,205,041

VARIABLE TUNED TRANSFORMER Filed Aug. 12, 1937 2 Sheets-Sheet 1 REASE H. A. MOORE ET AL VARIABLE TUNED TRANSFORMER ATTORNEY July 2, 1940.

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Patented July 2, 1940 UNITED STATES PATENT OFFICE 2,206,041 VARIABLE TUNED TRANSFORMER Harold A. Moore and John B. Moore, Riverhead, N. Y., assignors to Radio Corporation America, a corporation of Delaware Application August 12, 1937, Serial No. 158,756 '7 Claims. (Cl. 178-44) This invention relates to a new and novel ar- In this specific embodiment of variable bandrangement of tuned transformers; and more parwidth intermediate frequency transformer, the ticularly to tuned transformers having a variable band-width will not be continuously variable (alband-width suitable for use in intermediate frethough it is possible by a slight modification of quency amplifier ystems of radio receivers, the structure elements to make it SO) but the The object of this invention is to provid a construction will be such that a choice of two simple means of obtaining two or more band or more band-widths is available. The electrical widths, each having the o ti m shape of constants of the circu't for each band-width are lectivity characteristics, and each being centered predetermined. Vacuum tube Al has its output around the same midband frequency, 001111801366. t0 the primary C011 Ll 0f the interri t th d of changing th b didth mediate frequency transformer M. Connected in of tuned transformers have been such as to ob- Shunt With 0011 Li 5 a fiXed capacity C, a trimtain the optimum shape of the frequency charming condenser C2, a resistance RI, and a switch acteristic at only one value of band-width. Such X Which is arranged to Switch in an additional adjustments were either inaccurate or laborious. Shunt resistance R2 and a pac ance C3- A The present invention makes it possible to Secondary @011 L2 is shunted y a fixed pa quickly adjust the transformers to give the opfiance a trimming ondenser C5 and termitimum frequency characteristic at each of the hating resistances R3 and R A additional two or more accurately predetermined values of Shunt Capacitance 5 and resistance R5 are shown band-width. Briefly, the selection of the desired as being capable of being switched in circuit by band-width in accordance with this invention is Switch Y connected to the ju n p int of reaccomplished by t movement of a knob which sistances R3 and R4, at which point a connection simultaneously sets the mutual inductance beis made to the grid input of Va uum tube A2.

tween the primary and secondary to a prede- The particular circuit arrangement shown by i termined value and either cuts in or out addi- Fig 1 0f the drawings P es the same volttional damping resistance and tuning capaciage gain n both band-widths. This is accomtancg The bject of cutting in and t t plished by the combination of loading resistors preadjusted fixed tuning capacitance and load- El, R3, R3, R4 and 111 Order to p the ing resistances is t k th constants of t characteristic centered around the same midcircuit such that for both conditions of bandb frequency F0, as shown in s- 2 of the width the midband frequency of the selected band drawings, When the Coupling between Coils Ll will be constant and the response curve will be and L2 is Changed, the d d oapacitances C3 essentially uniform (fiat topped) throughout the and C5 are Switched Onto the primary a d secuseful pass band. ondary circuits, respectively, at the same time This invention will best be understood by reas are the added resistances R2 and R5. For eX- ferring to the accompanying drawings, in which: ample, in the graphic p se tation shown in Fig. 1 is a schematic circuit diagram of the a 2, Fl represents a two yc e per second improved tran former aryangement; band-width and F2 represents a four kilocycle Fig. 2 is a diagram giving a graphic represenper second band-width. If the added capacitation of two banwwidths; tances C3 and C6 were not simultaneously Fig. 3 is a plan view of the apparatus for cswitched in by switches X and Y, when the coil complishing the purpose of this invention; Coupling Changed, the b d-W dth Would be Fig. 4 is a side view of Fig. 3, partly in section offset from the mid-band frequency F0, as is giving a longitudinal view of t 11 oupling indicated by the dash lines F3, which would be arrangement; undesirable from an operating standpoint. Fig. 4A is a plan view of a portion of Fig. 4 Referring now to Figs. 3, 4 and 5, the meshowing the variable and fixed tuning condenser chahichl arrangement of the ppa s is shown. arrangement; while The circuit elements are all contained within a 5 is an uncl rside elevation of Figs. 3 and 4. suitable shielding can I and are mounted upon Referring now to Fig. l of the drawings, a a base of insulating material 2. The fixed coil 5 circuit diagram of a single amplifier stage of a 3 is shown supported on base 2 by an insulating tuned transformer is shown, such as is used in rod 4 which has one side cut away for mountthe intermediate frequency amplifiers of radio ing. The movable coil 5 is mounted upon an receivers, and is particularly adapted to what is insulating rod 6, which is cut away on both sides known as commercial type receiving equipment, to provide retention means for sliding engagemid-band frequency, as in the case of the narrow band adjustment. These positions were previously described with reference to Fig. 2.

l!) fastened by nuts provided with a pro ecting guide piece i 3 which shown in the drawings, it is possible to provide slides or telescopes within a bore M of rod 4, three or more band-widths by adding additional ensuring perfect alignment for coils 3 and 5. A switch contacts and contact members; also, a plate [5 also of insulating material, is fastened detent action should be provided for the various to the underside of base 2. This plate serves the coupling positions.

dual purpose of retaining rod 6 in position and What is claimed is: also acts as a sub-base for the switch bearing 1. A tuned transformer having means for sil6, To limit the motion of carrier member 6 multaneously changing coupling and electrical and coil 5, two adiustable stop members H and circuit constants, compiising a fiat base inembei are D d p member is S w ma fixed coil secured to said base member by an iting the movement of 8011 5 In ts extreme p0s1- insulating rod having a centi a1 bore, a slot in said tion, which limits the coil 5 in its loose coupled base, an insulating movable member arranged to D t H- S p m m 111111178 0011 5 in 1% have one end slide in said slot, a movable coil se- 01088 pled position. Suitable 1 15 '9 are p cured to the central portion of said movable memvided for guiding mem e s and in Slots ber, the other end of said movable member ar- 0, as showno Va y t am n of movement ranged to slide in the bore of said insulating rod of coil 5 set screws 2| a e loosen d, d When to ensure perfect alignment for said coils, an op the e d Coupllng 100511710115 are Secured Stops crating knob, and a linkage system arranged ben ar S ure y sten d n thell tween said operating knob and said movable gienagsigioil lsi bylsset scrgws pillh g ig m l it member to move said coil in coupling relation- & C01 15 ac 0m 5 e y a S 0 e shi with said fixed coil. d w c 5 actuated y a Shaft 33 a 25 A tuned transformer having means for sillnked f by a Spring member 74 Whlch multaneously changing coupling and electrical telmmates In a Spllal around Shaft 23 A ball circuit constants comprising a container foi said and socket arrangement 25 is secured to shaft 23 transfo mer having located thevem a flat base and llnks together a second and socket all"- member a fixed 1 secu ed to sand base mem rangement 26 by a P A crank Shaft 23 her by an insulating rod having a central boie, a a bearmg the end of the shaft slot in said base, an insulating movable membei terminating in an operating kn b A SWltch arianged to have one end slide in said slot, a movis provided for connecting in circuit resistance a 19 c011 Seemed to the seminal portlon of Said condenser C3 reslstance R5 and Pondenser movable member, the other end of said movable dlsc 32 g g s i i g g :5; member arranged to slide in the bore of said ing Contact segments 32 and 3 Contacts sullating rod totensuie pgrfeclalignnliient foi 234d cois, an opera mg no an a in age sys em 40 g g jzfi pigg i g gg i g ggg g i fi ig; arranged between said operating knob and said switch is rotated to the closed position. which is 2;;igiififififif g ggg jg c011 m Couphng the position of maximum coupling. Other parts 3 A tuned transformer havmg means for SP 32 225 fg gg g gg f ggs g gfi f g multaneously changing its coupling and electrical condensers CI to C6 inclusive, and the associat ed clrcmt Constants compnsmg a Centamel havresistances R to R5 inclusive ing located therein a flat base member, a fixed The operation of h improved tuned tram? coil secured to sa d base member by an insulating former is as follows: hen control knob 3g rod, a slot in said base, an insulating movable turned, for example, from the narrow band to the member arranged to have one end shde m Bald wide band position, the following functions are slot amovable 001] secured to the Gen-tidal poltmn performed of said movable member, an operating knob a (1) The coupling between cons 3 and 5 1S linkage system arranged between said operating creased by moving them Closer together Thlslm knob and said movable member to move said creases the percentage coupling and mutual inmovable 0011 such a manner as to Change lbs ductance to a predetermined value which is re- Coup 1mg relatlonshlp Wlth sald fixed c011 and a quired for the der band. switch contact member secured to said base and (2) Resistance R5 is shunted across a portion coupled to Sald Imkage System for .swltchmg m of the Secondary circuit termmatmg Voltage db or out of the circuit a plurality of resistances and vider, consisting of resistances R3 and R4 by cfmacltance elements when said coup 1mg 18 means of switch Y, completing the circuit becnanged tween contact members 34. This compensates A tuned transmnnfi Y means for for the change in gain caused by the change of multaneously changing coupling and electrical transformer impedance when the percentagp circuit constants comprising a fixed and a mov- W coupling is changed The total eiTective damping able 0011 both of Whlch are mounted on a o fol the Wlde band 18 then made up by shunting mon base plate by tworod-like members one of another resistance R2 across the primary circuit telescopes W1th1n the other means for by switch X completmg the Circuit between am moving said movable coil in coupling relationship th pair of Contact members 34 with said fixed 0011 said means comprising an 3 Capacitances 5 and 3 are switched on operating knob, a link system connecting said with the resistances 5 and R2 as mentioned movable coil and said operating knob in operaabove. The added capacitances increase the eft engagement, a fi D guide m e for fective total capacitance across each coil. The guldlng Sald movable C011, and a SWltch Contact capacity of condensers C6 and C3 are of such member mounted 011 said base member d C011- value as to make the frequency characteristic of pled to said link system for switching in shunt the wide band position center about the same with at least one of said coils a resistance and capacitance element when the coupling of said coils is changed.

5. A tuned transformer having means for simultaneously changing coupling and electrical circuit constants comprising a base member by two rod-like members one of which telescopes within the other, a fixed coil secured to said base member, a slot in said base, a movable member arranged to slide in said slot, a movable coil secured to the central portion of said movable member, an operating knob, a linkage system arsaid operating knob and said movable member to move said coil in coupling relationship with said fixed coil, and a switch contact member said base plate and coupled to said link system for switching in circuit a plurality of resistances and capacitances when the coupling of said coils is changed.

6. A tuned transformer having means for simultaneously changing coupling and electrical circuit constants, comprising a base member, a fixed coil secured to said base member by an insulating rod having a central bore, a slot in said base, an insulating movable member arranged to have one end slide in said slot, a movable coil secured to the central portion of said movable member, the other end of said movable member arranged to slide in the bore of said insulating rod to ensure perfect alignment for said coils, an operating knob, and a linkage system including a ball and socket member arranged between said operating knob and said movable member to move said coil in coupling relationship with said fixed coil.

'7. A tuned transformer having means for simultaneously changing coupling and electrical circuit constants, comprising a base member, a fixed coil secured to said base member by an insulating rod having a central bore, a slot in said base, an insulating movable member arranged to have one end slide in said slot, a movable coil secured to the central portion of said movable member, the other end of said movable member arranged to slide in the bore of said insulating rod to ensure perfect alignment for said coils, an operating knob, and a linkage system including a rotatable shaft on said base, a spring member secured to said shaft, a ball and socket member arranged between said operating knob and said movable member to move said coil in coupling relationship with said fixed coil.

HAROLD A. MOORE. JOHN B. MOORE. 

